Spacecraft structures are very difficult to design and construct due to the many and often conflicting requirements. For example, the spacecraft structure must have sufficient strength to withstand the forces imposed upon it when it is launched into orbit. However, the launch vehicle cost per pound of in orbit spacecraft places definite weight limitations on the spacecraft. Orbiting spacecraft are also subjected to thermal gradients from the sun and the installed electrical equipment places further limitations on the types of materials that can be used in the structural architecture. These problems are compounded with smaller spacecraft that are typically launched on the smaller spacecraft that are typically launched on the smaller expendable launch vehicles which impose substantial geometric constraints.
The solutions to these problems associated with the construction of previous spacecraft structures have involved long lead time for design, analysis, and fabrication. Use of advanced high performance materials is often investigated as one means of solution. However, although such materials offer optimized weight, strength, and stiffness they also introduce high cost, long lead times, fabrication and integration problems, as well as less than optimal thermal and orbit degradation problems.
Typical spacecraft structures consist of a frame that supports most of the main loads and the rest of the structure is attached to this frame. This type of construction occupies considerable volume for the structure itself that might be more profitably used for the spacecraft payload. This type of construction may also make it more difficult to distribute the spacecraft payload in the desired manner.
Typically, spacecraft are constructed to a specific design for a specific mission. This involves advanced planning coupled with high non-recurring engineering costs, extended fabrication schedules and the requirement to obtain advanced materials that require special handling and fabrication processes and techniques.
In view of these past problems there is a definite need for a spacecraft structure that provides the required stiffness and strength to weight ratios without the need to use "advanced" materials. There is also a need for a spacecraft that provides a large volume for the payload and versatility for payload positioning at any time during the fabrication cycle.